Highly Flexible Polylactide Food Packaging Plasticized with Nontoxic, Biosourced Glycerol Plasticizers

Polylactide (PLA) is a promising biosourced and biodegradable polymer substitute for traditional petroleum-based products. Despite its recognized potential, its widespread adoption is restricted by its brittleness and low ductility and, thus, to enhance its material properties, plasticizers must be blended with PLA to lower the glass transition temperature (T-g) and impart flexibility into the blend. As such, this work focused on the synthesis of a family of biosourced plasticizers for applications in flexible food packaging using glycerol, succinic anhydride, and alcohols of varying chain lengths. The effect of the chemical structure on plasticization performance, migration, blend morphology, and toxicity was evaluated and compared to the commercial plasticizer acetyl tributyl citrate. Plasticizer/PLA blends were prepared using solvent-casting as well as melt-mixing to produce thin films and bulk specimens. At loadings of 20 wt %, improved flexibility (up to 435% elongation) was observed in films with the glycerol plasticizers relative to neat PLA (6% elongation), while T-g's were reduced by up to 45 degrees C from that of neat PLA (T-g similar to 60 degrees C). Phase morphologies evaluated with scanning electron microscopy showed good incorporation of the plasticizers into the PLA matrix. Leaching behavior of the plasticized blends was evaluated in different food simulants and showed that plasticizers composed of branched or longer alkyl chains produced two- to sixfold lower migration rates compared to those with short alkyl chains. Finally, plasticizer candidates were shown to be nontoxic and did not impact HepG2 cell viability over a period of 7 days in an in vitro mammalian cell assay.

Automated summary

This study focused on the synthesis of a family of biosourced plasticizers for applications in flexible food packaging. These plasticizers, when blended with PLA, enhance its flexibility and reduce the glass transition temperature without impacting material performance. The experimental results showed that the plasticizers had an effect on the leaching rate and phase morphology of PLA, and the candidate plasticizers demonstrated non-toxicity in cell assays.